The present invention relates to an alternating actuation device for a needling machine.
The present invention also relates to such a needling machine provided therewith, used for mechanically consolidating a fibre fleece coming, for example, from a crosslapper.
The known needling machines comprise a support called a board on which needles are fixed. Alternating actuation devices, having rods and cranks, impart an alternating motion to the board in order that the needles traverse the fibre fleece at a rate which can vary between 1000 and 2000 strokes per minute during production.
Additional devices also make it possible to regulate the flow of fibres entering and leaving the machine with or without drawing and at speeds chosen according to the striking rate and the number of strokes per minute, equivalent to the number of alternating movements of the needles per minute.
DE-A-1 660 778 describes an actuation device in which a crankshaft supported by four bearings drives the needle board with an alternating motion by the intermediary of two connecting rods. A bearing is shown on each side of each connecting rod in a diagrammatic way and without any corresponding description.
DE-A-2 111 496 describes successive crankshafts disposed along an upper beam of the needling machine. Each crankshaft end is supported by a bearing. In another arrangement, the crankshafts, parallel instead of being aligned, are disposed transversely with respect to the beam. Considering the limited width of the beam, the bearings are brought towards the centre and are thus positioned between a central equilibration means and each actuating eccentric for actuating the connecting rods.
These known devices operate in free air and are lubricated with grease.
Actuation devices are also known which are mounted in a sealed crankcase and which are lubricated with oil. In this case the crankshaft, oriented in the direction of the width of the fleece to be needled, is supported in rotation by two bearings mounted in openings provided in two opposite end walls of the crankcase. Between the two bearings, the crankshaft comprises two eccentrics forming cranks, each one of them connected to an actuating connecting rod, and supports equilibration means of the inertia and/or counterweight type. The crankshaft emerges from the crankcase through each of the bearings in order to be connected to a driving source and/or to another coaxial crankshaft, belonging to another actuation device.
The known actuation devices are subjected to high alternating loads which generate dangerous vibrations and noise. The force necessary to make the needles penetrate into the fleece is high. This results in generous dimensioning of the moving parts of the alternating actuation devices. The result of this is that large inertial forces are added to the intermittent force of penetration and extraction of the needles, and that the reciprocating actuation devices are subjected to substantial mechanical stresses and deformations. Finally, it is necessary to limit the striking rate.
The purpose of the invention is to increase the striking rate permitted to needling machines and/or to reduce the harmful effects of the alternating loads at a given rate.